Systems for tracking a position and an orientation of a rigid device in relation to an object and in relation to image data of the object are used in many types of applications. One application in which such systems are commonly used is in the field of optically navigated surgical procedures. In this case, the navigation of the rigid device is typically based on optical tracking (e.g., using visual markers rigidly attached to the device and an optical localization system detecting the visual markers).
In some applications it is desirable to track a flexible device (e.g., an endoscope, a catheter or a flexible needle) which is inserted into the object. In this case, the tracking of a shape of the flexible device within the object can become relevant in order to assist in executing a particular procedure. The tracking allows, for example, to improve the accuracy of a surgical procedure (to prevent erroneous steering of the flexible device) and to minimize the invasiveness thereof. One technology which is commonly used in this regard is the so-called fiber shape matching technology. This technology uses an optical fiber which is attached to or integrated in the flexible device to be tracked. A plurality of bending sensor units, such as fiber Bragg grating sensors, is arranged at different portions along a length of the optical fiber and provide bending information from said portions. By means of an interpolation of the bending information, the shape of the flexible device is reconstructed and may thus be tracked.
If the device is inserted into a highly curved and branched object, such as a tubular structure, a high number of bending sensor units needs to be arranged along the optical fiber to achieve sufficient reconstruction accuracy. To avoid the high number of bending sensor units, WO 2012/158324 A2 suggests reconstructing the shape of the flexible device by registering the bending information provided by a plurality of bending sensor units with a three-dimensional model of the object.